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XTR111-2EVM

Other Parts Discussed in Thread: XTR111-2EVM, XTR111

Hello,

I am trying to use the XTR111-2EVM as a current source to power the specimen. A sinusoidal wave oscillated at 100Hz~2000Hz will be the input signal. The peak-to-peak amplitude ranges from 0.5V~1.5V. I am wondering whether the XTR111-2EVM is able to deal with the negative portion of the input sinusoidal signal and what the linear output range of the XTR111-2EVM is.

Thanks in advance.

Best,

Lei

  • Hi Lei ,

    The XTR111 cannot handle the negative voltages

    As mentioned in the page number 3 of XTR111 datasheet 

    Input voltage can only swing from 0 12V

    The linear output range for XTR111 is 0.1 mA to 25 mA

    Also i could help you a little more if you can share with me the end objective which we are trying to achieve here ?

    can you please share some more information on

    what is the output are looking for ?

    what is the load connected at the output of XTR111?

    Thank you 

  • Hi Shreenidhi,

    Thank you for your reply. Please find enclosed the schematic diagram of our setup.

    We would like to measure the thermal conductivity of our sample using the 3 omega method.  A home-made voltage-to-current source converter was used to power the sample, as can be seen in the diagram. We have to offset the sine signal generated by the function generator a little bit so that the operational amplifier can handle the negative portion of the signal. However, it's not easy for the current source to produce linear signals. We can even detect 2 omega signals in the circuit and we suspect that's attributed to the current source. This is why we want to use the XTR111-2EVM to replace our previous current source.

    Could you help me on this issue, please?

    Thanks,

    Lei

    Schematic Diagram.tif

  • hi Lei ,

    Thank you for your  reply

    Please correct me if I am wrong , I believe the 3 omega method for measuring thermal conductivity requires a current to be injected into the specimen which is a sine wave with zero offset. i.e. you would be needing a circuit which can provide bi directional current into your specimen  and The problem you are currently  facing with functional generator is that it is not linear and hence you are not able to measure accurately the 3 omega signals ( 3 times fundamental frequency ) in your sensing circuit.

     

     

    If there is a requirement of bidirectional current as mentioned above  the XTR111 is out of the question . As it can only source currents into the load

    You can have a look at the design below which will help you to design a voltage to bi directional current 

    You can use the  circuit shown in the ti design above with out the bootstrap 

    Thank you

     

  • Hi Shreenidhi,
    Thanks for your help.
    One more question: if the XTR111-2EVM is powered by a dual polarity power source, say -5V and +5V, is the XTR111-2EVM able to handle the negative signals?
    Best,
    Lei
  • Hello Lei , 

    The supply  voltages for XTR111 as specified in the datasheet need to be 8V to 40V

    So you cannot apply supply +5 and -5 to the EVM

    also providing a negative input signal to the Vin of XTR111 should be strictly avoided

    Thank you